Access point signal estimation

ABSTRACT

Examples relate to access point signal estimation. In one example, a computing device may: receive a first pathloss value in a first frequency, the first pathloss value indicating a difference in transmit power of a particular access point and a received signal strength observed by a first access point; receive a second pathloss value in the first frequency, the second pathloss value indicating a difference in transmit power of the particular access point and a received signal strength observed by a second access point; receive a third pathloss value in a second frequency, the third pathloss value indicating a difference in transmit power of the particular access point and a received signal strength observed by the second access point in the second frequency; and generate, using the first, second, and third pathloss values, an estimated pathloss between the first access point and the particular access point in the second frequency.

BACKGROUND

Wireless network communications devices, such as personal computers,mobile phones, Wi-Fi access points, and cellular network access points,transmit data across wireless networks. To provide wireless access to alarge area, multiple access points are often spread out with the intentto provide network access to a target area, such as an office building,a park, or a retail store. Access point placement may have a significantimpact on the quality of wireless communications and may also affectuser behavior and satisfaction.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description references the drawings, wherein:

FIG. 1 is a block diagram of an example computing device for accesspoint signal estimation.

FIG. 2 is an example diagram depicting access point signal estimationfacilitated by an access point management device.

FIG. 3 is an example data flow depicting access point signal estimationat an access point.

FIG. 4 is a flowchart of an example method for access point signalestimation.

DETAILED DESCRIPTION

Wireless access points generally use antennas to emit wireless signalsthat can be received and used by other wireless devices. Wireless signalstrength may depend on a variety of factors, such as the power output ofa wireless access point, wireless congestion from other wirelesscommunications, and interference from electrical sources and physicalobjects. To increase wireless coverage for an area, multiple wirelessaccess points are often deployed near each other in order to increasewireless availability and signal strength for devices that make use ofthe network. In addition, wireless access points often use multipleradios in different frequencies and communicate using different channelswithin those frequencies, e.g., in a manner designed to reduceinterference between access points.

Various techniques may be used when deploying multiple access points ina particular location in a manner designed to improve the users'wireless experience. For example, an administrator may physically spaceaccess points throughout a building in a particular pattern. However,physical obstructions and electronic devices, among other things, maycause interference that makes physical placement of access pointsdifficult to do manually while maintaining a desired quality of wirelesscoverage. Wireless signal strength measurements between access pointsmay be a useful feature for placing wireless access points, e.g., areceived signal strength measurement (RSSI), measured in dBm, or apathloss measurement, measured in dB, may provide an indication of thesignal strength between wireless access points. RSSI and pathloss may beused, for example, to determine whether access points are too close ortoo far from one another, and various techniques may be used that relyon the signal strength measurements to manage the access points. Forexample, the signal strength measurements may be used to manually adjustphysical placement of access points or adjust output/transmit power ofthe wireless radios.

Wireless access points are capable of automatically discovering oneanother using techniques such as off-channel scanning for beacons ofother access points and sending over-the-air frames for other accesspoints to discover. For example, a 2.4 GHz radio broadcasting on channel11 may send out a beacon packet, which may be discovered by a secondaccess point that is listening for beacon packets at the same frequencyand on the same channel. However, with this type of discovery, accesspoints often change their home wireless channel to scan for other accesspoints communicating in the off-channel. Depending on the frequency withwhich access points change channels, which may be performed every otherframe in a round robin style, one access point may miss a beacon packetif it is scanning a particular channel while another access point isalso performing off-channel scanning. For example, the 2.4 GHz radiobroadcasting its beacon packet on channel 11 may frequently scan other2.4 GHz channels in an attempt to identify other 2.4 GHz radios.However, a second 2.4 GHz radio broadcasting its beacon packet onchannel 1 may be doing the same thing, and the access points may missthe beacon packets if they are both off-channel, failing to discover oneanother.

When using multiple radios, e.g., a 2.4 GHz radio and a 5 GHz radio,different channels may be used on each radio. This may cause accesspoint discovery techniques, like the off-channel scanning describedabove, take longer, especially at a frequency where many channels areavailable for wireless communications. To facilitate the access pointdiscovery process and obtain signal strength measurements that can beused, for example, to facilitate access point placement and poweroutput, access points using multiple radios may be configured toestimate signal strength.

By way of example, three access points may be within range of oneanother and communicating on both 2.4 GHz and 5 GHz radios. A firstaccess point may have determined a pathloss value—the reduction in powerof wireless signals as they propagate through space—between the firstaccess point and the second access point in the 2.4 GHz spectrum usingnormal off-channel discovery. E.g., the first access point may havescanned for and found the second access point's beacon packet,determined the RSSI for the beacon packet, and used the power output ofthe second access point to determine the pathloss. An example pathlossvalue is 100 dB. However, the first access point may not yet havediscovered the 5 GHz radio of the second access point.

A third access point which has discovered and determined pathloss valuesfor both the 2.4 GHz radio and the 5 GHz radio of the second accesspoint, may communicate its pathloss values to the first access point.For example, the third access point may provide data to the first accesspoint indicating that its pathloss to the second access point is 80 dBin the 2.4 GHz frequency and 100 in the 5 GHz frequency. Using the threepathloss values, the first access point may estimate its pathloss to thesecond access point in the 5 GHz frequency. For example, the ratio ofthe 2.4 GHz pathloss to the 5 GHz pathloss observed by the third accesspoint is 80:100, or 4:5. When access points are deployed in anenvironment similar to one another, the first access point may assumethe same or a similar ratio would likely apply to its own pathlossvalues. Using the example ratio of 4:5, the first access point mayestimate that its pathloss to the 5 GHz radio of the second access pointis 125 dB, e.g., 4:5=100:125. As noted above, the estimated pathlossvalues may be used to facilitate access point placement and poweroutput, e.g., in a manner designed to improve user experience. Furtherdetails and examples of estimating wireless signal strength aredescribed in further detail below.

Referring now to the drawings, FIG. 1 is a block diagram 100 of anexample computing device 110 for access point signal estimation.Computing device 110 may be, for example, a server computer, a personalcomputer, a wireless router, a cellular device, such as a cell phone, orany other similar electronic device capable of processing data. In theexample implementation of FIG. 1, the computing device 110 includes ahardware processor, 120, and machine-readable storage medium, 130.

Hardware processor 120 may be one or more central processing units(CPUs), semiconductor-based microprocessors, and/or other hardwaredevices suitable for retrieval and execution of instructions stored inmachine-readable storage medium, 130. Hardware processor 120 may fetch,decode, and execute instructions, such as 132-138, to control processesfor access point signal estimation. As an alternative or in addition toretrieving and executing instructions, hardware processor 120 mayinclude one or more electronic circuits that include electroniccomponents for performing the functionality of one or more instructions,such as a field programmable gate array (FPGA) or application specificintegrated circuit (ASIC).

A machine-readable storage medium, such as 130, may be any electronic,magnetic, optical, or other physical storage device that contains orstores executable instructions. Thus, machine-readable storage medium130 may be, for example, Random Access Memory (RAM), non-volatile RAM(NVRAM), an Electrically Erasable Programmable Read-Only Memory(EEPROM), a storage device, an optical disc, and the like. In someimplementations, storage medium 130 may be a non-transitory storagemedium, where the term “non-transitory” does not encompass transitorypropagating signals. As described in detail below, machine-readablestorage medium 130 may be encoded with executable instructions: 132-138,for access point signal estimation.

As shown in FIG. 1, the hardware processor 120 executes instructions 132to receive a first pathloss value in a first frequency, the firstpathloss value indicating a difference in transmit power of a particularaccess point and a received signal strength observed by a first accesspoint. For example, the computing device 110 may be a server computerthat is responsible for managing a network of wireless access points.The first pathloss value, e.g., 100 dB in the 5 GHz frequency, may beprovided to the server computer by a first wireless access point managedby the server computer. In some implementations, the particular accesspoint may be included in the computing device 110.

The hardware processor 120 executes instructions 134 to receive a secondpathloss value in the first frequency, the second pathloss valueindicating a difference in transmit power of the particular access pointand a received signal strength observed by a second access point. Forexample, the second pathloss value, e.g., 120 dB in the 5 GHz frequency,may be provided to the example server computer by a second wirelessaccess point managed by the server computer.

The hardware processor 120 executes instructions 136 to receive a thirdpathloss value in a second frequency that is different from the firstfrequency, the third pathloss value indicating a difference in transmitpower of the particular access point and a received signal strengthobserved by the second access point in the second frequency. Forexample, the second frequency may be the 2.4 GHz frequency. The thirdpathloss value, e.g., 90 dB in the 2.4 GHz frequency, may be provided tothe example server computer by the second wireless access point managedby the server computer.

In some implementations, the first, second, and/or third pathloss valuesmay be average pathloss values, e.g., determined by taking an averageobserved pathloss over a certain period of time. This feature may beuseful, for example, in situations where signal strength varies overtime. The periods of time used may vary, e.g., an average over seconds,minutes, hours, or days.

The hardware processor 120 executes instructions 138 to generate, usingthe first pathloss value, second pathloss value, and third pathlossvalue, an estimated pathloss between the first access point and theparticular access point in the second frequency. In someimplementations, the estimated pathloss is generated in such a way thata ratio of the first pathloss (100 dB) to the estimated pathloss isproportional to a ratio of the second pathloss (120 dB) to the thirdpathloss (90 dB). Using the example pathloss values above, and an exactratio proportion, the estimated pathloss would be 75 dB in the 2.4 GHzfrequency, e.g., 100:75=120:90. One example formula for performing theestimation is to divide the third pathloss (90 dB) by the secondpathloss (120 dB), and multiply the result by the first pathloss (100dB). This example formula also results in an estimated pathloss of 75dB, e.g., (90/120)*100=75. The actual formula used to generate theestimated pathloss may vary and, in some implementation, may introduceuse an uncertainty value, e.g., to provide a margin for error in theestimate.

In some implementations, additional pathloss values from other accesspoints may be used to estimate pathloss between the first access pointand the particular access point. For example, an additional access pointmay provide fourth and fifth pathloss values to the computing device110, e.g., 110 dB and 80 dB in the 5 GHz and 2 GHz frequencies,respectively. The fourth and fifth pathloss values may be used whengenerating the estimated pathloss and/or to adjust the estimatedpathloss. For example, a second estimated pathloss may be calculatedusing the pathloss values provided by the additional access point. Usingone of the example formulas above results in an estimated pathloss of 73dB, e.g., (80/110)*100=˜72.73. In some implementations multipleestimated pathloss values may be used, e.g., by averaging, to determinethe pathloss estimate. By averaging the two example pathloss values of75 dB and 73 dB, an estimated pathloss of 74 dB may be determined for2.4 GHz signal between the first access point and the particular accesspoint.

While the examples above use the 2.4 GHz and 5 GHz frequencies, anyother frequencies may be used. In addition, pathloss may be estimatedfor wireless access points that may use more than two radios in asimilar fashion. While pathloss values are used for wireless signalstrength estimation, other values, such as RSSI, may also be used.Pathloss values may be determined by each access point individually, bya computing device that manages the access points, or a combinationthereof.

FIG. 2 is an example diagram 200 depicting access point signalestimation facilitated by an access point management device 250. Theaccess point management device 250 may be a computing device, such asthe computing device 110 of FIG. 1. The example diagram also includesfour access points: AP1 210, AP2 220, AP3 230, and Target AP 240. In theexample diagram 200, a signal strength measurement—RSSI in thisexample—is estimated between AP1 210 and Target AP 240 in the 5 GHzfrequency using RSSI measurements from AP2 220 and/or AP3 230.

For example, the access point management device 250 may be provided withthe RSSI measurements recorded by each of the access points. Using anexample formula provided above and the RSSI values of AP2 220, theestimated RSSI between AP1 210 and Target AP 240 in the 5 GHz frequencyis −117 dBm, e.g., (−100/−60)*−70=˜−116.67. Using the same exampleformula and the RSSI values of AP3 230, the estimated RSSI between AP1210 and Target AP 240 in the 5 GHz frequency would be −92 dBm, e.g.,(−105/−80)*−70=−91.875. In an implementation where an average ofestimated RSSI values is used to estimate RSSI, the average estimatedRSSI using the example values above is approximately −105 dB. As notedabove, other formulas may be used to determine estimated signalstrength, and when using multiple access points, other methods foradjusting an estimate or generating an estimate may be used, e.g., usingthe average, the median, or some other value.

In some implementations, access points used to estimate signal strengthmay be weighted, or preferred, when used to determine an estimatedsignal strength measurement. For example, a network administrator mayknow that AP2 220 is in the same room of a building that AP1 210 is in,and that AP3 230 is in a different room on a different floor of adifferent building. Using this knowledge, an administrator may choose toprefer the estimate provided by AP2 220 rather than AP3 230. As anotherexample, the administrator may use both estimates, but weigh theestimate associated with AP2 220 more heavily than the estimateassociated with AP3 230.

FIG. 3 is an example data flow 300 depicting access point signalestimation at an access point, e.g., AP1 310. In this example data flow300, an access point performs the signal estimation, e.g., rather thanthe estimation being performed by a separate computing device. In theexample data flow 300, access points AP2 320 and AP3 330 providepathloss values to AP1 310, The provided pathloss values are the valuesin the 2.4 GHz and 5 GHz frequencies, observed between each respectiveaccess point and Target AP 340. In some implementations, some or all ofthe pathloss values associated with AP2 320 and AP3 330 may be providedby a computing device that is separate from the depicted access points,e.g., by an access point management device.

In the example data flow 300, AP1 310 has observed its own pathloss toTarget AP 340 in the 2.4 GHz frequency but has not yet determinedpathloss to Target AP 340 in the 5 GHz frequency. This pathloss valuemay be determined using transmission data, e.g., a beacon packet thatwas sent by Target AP 340 and received by AP1 310. For example, AP1 310may have identified a beacon packet from Target AP 340 while performingoff-channel scanning in the 2.4 GHz frequency. An RSSI of −75 dBm mayhave been determined by AP1 310 upon receipt of the beacon packet, andthe beacon packet may have included data that indicated the transmitpower of Target AP 340, e.g., 20 dBm. Using the RSSI and transmit power,AP1 310 may determine a pathloss value of 95 dB between AP1 310 andTarget AP 340 in the 2.4 GHz frequency. In some implementations, thetransmit power of Target AP 340 may be provided to AP1 310 by a separatedevice, such as an access point management device.

Using the example pathloss values provided by AP2 320 and/or AP3 330 inthe example data flow 300, AP1 310 may determine an estimated pathlossbetween AP1 310 and Target AP 340 in the 5 GHz frequency. Using thevalues of AP2 320, for example, AP1 310 may estimate the pathlossbetween AP1 310 and Target AP 340 to be 114 dB, e.g., (120/100)*95=114dB. Using the values of AP3 330, AP1 310 may estimate the pathlossbetween AP1 310 and Target AP 340 to be 106 dB, e.g.,(100/90)*95=˜105.56. In situations where estimated pathloss valuescalculated using multiple access points are averaged, the estimatedpathloss between AP1 310 and Target AP 340 may be 110 dB.

FIG. 4 is a flowchart of an example method 400 for access point signalestimation. The method 400 may be performed by a computing device, suchas a computing device described in FIG. 1, e.g., in the form of anaccess point. Other computing devices may also be used to execute method400. Method 400 may be implemented in the form of executableinstructions stored on a machine-readable storage medium, such as thestorage medium 130, and/or in the form of electronic circuitry.

At a first access point and in a first frequency, transmission data froma particular access point is received (402). Transmission data may be,for example, a beacon packet sent by the particular access point using a2.4 GHz radio. The transmission data may information regarding theparticular access point, including—in some implementations—a transmitpower. The transmission data, e.g., the transmit power, may in someimplementations be provided by the particular access point indirectly,e.g., from an access point management device in communication with thefirst access point and the particular access point. When receiving abeacon packet from the particular access point, the first access pointmay also determine a signal strength measurement, e.g., an RSSI, for thebeacon packet.

Based on the transmission data, a first pathloss value is determinedthat indicates a difference in transmit power of the particular accesspoint and a received signal strength observed by the first access point(404). For example, in a situation where the transmit power of theparticular access point is 15 dBm, and the RSSI observed by the firstaccess point using the beacon packet was −65 dBm, the first pathloss inthe 2.4 GHz frequency may be the difference between the two, e.g., 80dB.

At the first access point, a second pathloss value is received that isassociated with the first frequency, the second pathloss valueindicating a difference in transmit power of the particular access pointand a received signal strength observed by a second access point in thefirst frequency (406), For example, a second access point may, directlyor indirectly using an access point management device, send a secondpathloss value of 90 dB in the 2.4 GHz frequency.

At the first access point, a third pathloss value is received that isassociated with a second frequency that is different from the firstfrequency, the third pathloss value indicating a difference in transmitpower of the particular access point and a received signal strengthobserved by the second access point in the second frequency (408). Forexample, the second access point may, directly or indirectly using anaccess point management device, send a third pathloss value of 130 dB inthe 5 GHz frequency.

As noted above, in some implementations, average pathloss values may beused. For example, the average pathloss over time may be more likely toprovide a more consistent and/or predictable pathloss measurement.

Using the first pathloss value, second pathloss value, and thirdpathloss value, an estimated pathloss is determined between the firstaccess point and the particular access point in the second frequency(410). For example, a pathloss value may be estimated by determining aratio of the first pathloss to the estimated pathloss as being equal toa ratio of the second pathloss to the third pathloss, resulting in anestimated pathloss of 116 dB, e.g., 80:116=90:130 when rounded.

In some implementations, additional pathloss values from additionalaccess points may be used to determine an estimated pathloss. Forexample, at the first access point, a fourth pathloss value may bereceived that is associated with the first frequency, the fourthpathloss value indicating a difference in transmit power of theparticular access point and a received signal strength observed by athird access point in the first frequency, and a fifth pathloss valuemay be received that is associated with the second frequency, the fifthpathloss value indicating a difference in transmit power of theparticular access point and a received signal strength observed by thethird access point in the second frequency. The estimated pathloss maybe adjusted using the fourth and fifth pathloss values. For example, asecond estimated pathloss may be determined and averaged with the firstdetermined pathloss estimate. As noted above, signal estimation may beperformed using a number of additional signal strength measurements froma number of other access points.

The foregoing disclosure describes a number of example implementationsfor access point signal estimation. As detailed above, examples providea mechanism for determining an estimated signal strength for an accesspoint using signal strength measurements of at least one other accesspoint.

We claim:
 1. A non-transitory machine-readable storage medium encodedwith instructions executable by a hardware processor of a computingdevice for access point signal estimation, the machine-readable storagemedium comprising instructions to cause the hardware processor to:receive a first pathloss value in a first frequency, the first pathlossvalue indicating a difference in transmit power of a particular accesspoint and a received signal strength observed by a first access point;receive a second pathloss value in the first frequency, the secondpathloss value indicating a difference in transmit power of theparticular access point and a received signal strength observed by asecond access point; receive a third pathloss value in a secondfrequency that is different from the first frequency, the third pathlossvalue indicating a difference in transmit power of the particular accesspoint and a received signal strength observed by the second access pointin the second frequency; and generate, using the first pathloss value,second pathloss value, and third pathloss value, an estimated pathlossbetween the first access point and the particular access point in thesecond frequency.
 2. The storage medium of claim 1, wherein a ratio ofthe first pathloss to the estimated pathloss is proportional to a ratioof the second pathloss to the third pathloss.
 3. The storage medium ofclaim 1, wherein: the first pathloss value is determined using anaverage pathloss over a first period of time; the second pathloss valueis determined using an average pathloss over a second period of time;and the third pathloss value is determined using an average pathlossover a third period of time.
 4. The storage medium of claim 1, whereinthe instructions further cause the hardware processor to: receive, forthe particular access point, a fourth pathloss value in the firstfrequency, the fourth pathloss value indicating a difference in transmitpower of the particular access point and a received signal strengthobserved by a third access point; and receive, for the particular accesspoint, a fifth pathloss value in the second frequency, the fifthpathloss value indicating a difference in transmit power of theparticular access point and a received signal strength observed by thethird access point, and wherein the estimated pathloss is adjusted usingthe fourth pathloss value and fifth pathloss value.
 5. The storagemedium of claim 4, wherein the estimated pathloss is adjusted by:generating a second estimated pathloss using the first pathloss value,fourth pathloss value, and fifth pathloss value; and averaging theestimated pathloss and the second estimated pathloss.
 6. The storagemedium of claim 1, wherein: the computing device is separate from theparticular access point, the first access point, and the third accesspoint, and the computing device is in communication with the particularaccess point, the first access point, and the third access point.
 7. Thestorage medium of claim 1, wherein the particular access point isincluded in the computing device.
 8. A computing device for access pointsignal estimation, the computing device comprising: a hardwareprocessor; and a data storage device storing instructions that, whenexecuted by the hardware processor, cause the hardware processor to:receive a first received signal strength indicator (RSSI) from a firstaccess point, the first RSSI being observed at a first frequency;receive a second RSSI from a second access point, the second RSSI beingobserved at the first frequency; receive a third RSSI from the secondaccess point, the third RSSI being observed at a second frequency thatis different from the first frequency; and generate, using the firstRSSI, second RSSI, and third RSSI, an estimated RSSI in the secondfrequency for the first access point.
 9. The computing device of claim8, wherein a ratio of the first RSSI to the estimated RSSI isproportional to a ratio of the second RSSI to the third RSSI.
 10. Thecomputing device of claim 8, wherein: the first RSSI value is determinedusing an average RSSI over a first period of time; the second RSSI valueis determined using an average RSSI over a second period of time; andthe third RSSI value is determined using an average RSSI over a thirdperiod of time.
 11. The computing device of claim 8, wherein theinstructions further cause the hardware processor to: receive, for theparticular access point, a fourth RSSI value in the first frequency, thefourth RSSI value indicating a difference in transmit power of theparticular access point and a received signal strength observed by athird access point; and receive, for the particular access point, afifth RSSI value in the second frequency, the fifth RSSI valueindicating a difference in transmit power of the particular access pointand a received signal strength observed by the third access point, andwherein the estimated RSSI is adjusted using the fourth RSSI value andfifth RSSI value.
 12. The computing device of claim 11, wherein theestimated RSSI is adjusted by: generating a second estimated RSSI usingthe first RSSI value, fourth RSSI value, and fifth RSSI value; andaveraging the estimated RSSI and the second estimated RSSI.
 13. Thecomputing device of claim 8, wherein: the computing device is separatefrom the particular access point, the first access point, and the thirdaccess point, and the computing device is in communication with theparticular access point, the first access point, and the third accesspoint.
 14. A method for access point signal estimation, implemented by ahardware processor, the method comprising: receiving, at a first accesspoint and in a first frequency, transmission data from a particularaccess point; determining, based on the transmission data, a firstpathloss value indicating a difference in transmit power of theparticular access point and a received signal strength observed by thefirst access point; receiving, at the first access point, a secondpathloss value associated with the first frequency, the second pathlossvalue indicating a difference in transmit power of the particular accesspoint and a received signal strength observed by a second access pointin the first frequency; receiving, at the first access point; a thirdpathloss value associated with a second frequency that is different fromthe first frequency, the third pathloss value indicating a difference intransmit power of the particular access point and a received signalstrength observed by the second access point in the second frequency;and determining, using the first pathloss value, second pathloss value,and third pathloss value, an estimated pathloss between the first accesspoint and the particular access point in the second frequency.
 15. Themethod of claim 14, wherein a ratio of the first pathloss to theestimated pathloss is proportional to a ratio of the second pathloss tothe third pathloss.
 16. The method of claim 14, wherein: the firstpathloss value is determined using an average pathloss over a firstperiod of time.
 17. The method of claim 14, further comprising:receiving, at the first access point, a fourth pathloss value associatedwith the first frequency, the fourth pathloss value indicating adifference in transmit power of the particular access point and areceived signal strength observed by a third access point in the firstfrequency; receiving, at the first access point, a fifth pathloss valueassociated with the second frequency, the fifth pathloss valueindicating a difference in transmit power of the particular access pointand a received signal strength observed by the third access point in thesecond frequency, and wherein the estimated pathloss is adjusted usingthe fourth pathloss value and fifth pathloss value.
 18. The method ofclaim 17, wherein the estimated pathloss is adjusted by: generating asecond estimated pathloss using the first pathloss value, fourthpathloss value, and fifth pathloss value; and averaging the estimatedpathloss and the second estimated pathloss.
 19. The method of claim 8,wherein: the second pathloss value and third pathloss value are providedby a computing device that is separate from the particular access point,the first access point, and the second access point.